You canât. Fixed-size compression is almost impossible in lossless mode and very hard in lossy mode, and PDFs may be a combination of both, with emphasis on the lossless side. Add to this this the âany PDF fileâ constraint and you have the impossible.
The only way to get around this problem is to either use the old ODT format, which is only available on the Macintosh and doesn't support ZIP format and lossy JPEG compression, or to convert from PDF to ODT. That takes time, time that's not available to us as software developers. We don't have sufficient time to do everything we'd like to do to make ODT better, and to do this in a timely fashion. PDF is a complex format, and it's important to have some tools for handling it to make our lives easier, while not losing compatibility with existing programs. While most ODT users will never need to deal with PDF format, we must make sure that this format is well-supported by all ODT-compliant software programs.